Dr. Denis O'Donnell

Looking for the causes of shortness of breath during exercise in people with mild COPD

Chronic obstructive pulmonary disease (COPD) is a leading cause of death and disability. An estimated 50% or more of smokers with mild COPD have not received the breathing test required to make the diagnosis and appropriate treatment is often delayed. We and others have provided evidence that some patients with mild COPD can experience troublesome shortness of breath and have a limited ability to undertake moderate physical activity.

It is becoming clear that such patients can have extensive damage (inflammation) to both the small airways and the surrounding network of blood vessels. This interferes with the ability of the lungs to take up oxygen from the air and to eliminate carbon dioxide from the blood. Because this damage develops slowly over time, the breathing apparatus can adapt to make sure that falls of oxygen in the arterial blood are avoided, even during the stress of exercise.

However, the downside is that their breathing becomes much more inefficient than in healthy patients: patients with mild COPD have to breathe 6-11 litres per minute (on average) more than healthy non-smoking “controls” to complete an identical physical task. Not surprisingly, these patients experience greater breathing discomfort during activity. "If we are to help these individuals, we need to better understand the nature of the gas exchange impairment in the lungs and the factors that cause this inefficiency of breathing in people with mild COPD," says Dr. O'Donnell.

This project should demonstrate that even patients with so-called “early” or mild COPD can have extensive damage of their small airways and blood vessels that are difficult to detect with traditional simple breathing tests. These results should provide a greater impetus for screening and early detection of this devastating disease.